1. Field of the Invention
The present invention relates to an image forming apparatus utilizing an electrophotographic system such as a copying machine or a facsimile and, more particularly, to an image forming apparatus having a unit detachably attachable to a main body of the apparatus and the unit.
2. Description of the Related Art
There has been conventionally an image forming apparatus utilizing an electrophotographic system in which a photosensitive drum, a cleaner, a development device, and the like disposed around the drum are unified as a so-called process cartridge, the unit being replaceable with respect to a main body of the image forming apparatus.
Like the process cartridge, a transfer belt unit constituted of a transfer roller and a belt member, which are adapted to transfer a toner image formed on an image bearing member (e.g., a photosensitive drum and an intermediate transfer belt) onto a transfer material, and a tension roller is a consumable. Therefore, the unit needs to be replaced with a new one when its life expires.
The image forming apparatus is provided with a counter which counts the speed of the belt member or the tension roller so as to notify a user of the need to replace the unit. When the count (i.e., a use history) of the counter reaches a predetermined value, an alert indicating the need to replace the unit concerned is displayed on a display in the image forming apparatus. Upon receipt of the alert, the user can replace the unit at a proper timing.
When the old unit is replaced with a new one, it is preferable that the past use history of the old transfer belt unit be reset, and then, a transfer voltage to be applied or the like be varied according to a new transfer belt unit. At this time, the user or a serviceman resets the use history on an operation portion. However, he or she may forget such work per se, and therefore, may not appropriately reset the use history.
In view of this, it is desirable that the new unit and the old unit be distinguishably detected, thereby securing the resetting work.
In the conventional image forming apparatus, there has been proposed a method for distinguishably determining a new process cartridge and an old process cartridge based on a fuse disposed therein. In this method, the old or new process cartridge is determined by detecting the electrically conducted state of the fuse in the process cartridge installed in the main body of the apparatus. When the process cartridge is determined to be a new one, the fuse is cut by predetermined initialization.
However, as described above, in the case where the fuse is cut by the predetermined initialization when the process cartridge is determined to be the new one, there have arisen the following problems.
For example, if a malfunction occurs in the image forming apparatus, it is necessary to identify whether the malfunction is caused by the main body of the image forming apparatus or the transfer belt unit. In this way, the serviceman who is requested to repair or investigate installs a new transfer belt unit in the main body of the image forming apparatus in question, and then, confirms operation, for the purpose of the diagnosis of the cause of the malfunction.
In this case, when the new transfer belt unit is installed in the apparatus, the image forming apparatus detects that the transfer belt unit installed is a new one, and then, performs the initialization of the transfer belt unit stored in the main body of the image forming apparatus. Then, the image forming apparatus adjusts parameters on the inside of a machine to values optimum for the new transfer belt unit, and further, cuts the fuse of the transfer belt unit. Thereafter, an image is output, and then, operation is confirmed. Here, in the case where the malfunction is caused by the old transfer belt unit, the old transfer belt unit is replaced with a new transfer belt unit.
In contrast, in the case where the malfunction is caused by the main body of the image forming apparatus, the above-described initialization erases the use history of the old transfer belt unit. In other words, even if the normal old transfer belt unit is installed again for use in the apparatus as a result of the investigation, the transfer belt unit cannot be used with optimum parameters.
In addition, the fuse of the transfer belt unit for use in troubleshooting has been cut already at the time of the installation irrespective of temporary use in investigating the cause of the malfunction. In this case, the transfer belt unit cannot be recognized to be a new one unless a fuse is replaced, thereby inducing many wastes.
In a configuration provided with a fuse member in the transfer belt unit, an electric contact portion is indispensable between the transfer belt unit and the main body of the apparatus, and therefore, the configuration becomes complicated in order to secure stable electric conductivity. Thus, an increase in the number of component parts inhibits cost reduction.